I ordered them at the start of this whole virus business so the delay wasn’t too bad then. I think they got to Norway in around 3 weeks, but I’ve heard things take longer now.
+1 in Shef's amp. I think I have a couple of those tubes floating around somewhere; it's a transmitting type (IIRC), but I forget the number/designator.
Edit: It definitely looks like an 826. Filament is 7.5 V at 4 A, 1,000 max plate voltage according to the datasheets.
Edit: It definitely looks like an 826. Filament is 7.5 V at 4 A, 1,000 max plate voltage according to the datasheets.
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I was looking around for a power transformer to use in an upcoming project and stumbled across the first thing I ever “designed” basically a floating paraphrase 6SL7 driving 6BL7 with no feedback. I put it together 30 years ago or so with nothing but old parts. I opened it up today and it was not as horrifying as I figured it would be but still entertaining enough. I remember just swapping secondary leads on the on the output transformers until it sounded right with 8 Ohm speakers. Still not even sure what those transformers are or what their impedance ratio was. So…. for your viewing pleasure, here are some photos of my first hack job 
Attachments
This my latest attempt at the 4s universal preamp.
In it I use off board toroidal trannys back to back for my HT. The transformer you can see provides 9v ac to the regulated 6.3v supply for the heaters.
I have an nos mullard 12au7 and Russian ft3 teflon caps for the output.
It has been teamed up with two dual mono lm3886 amps that power my two way open baffles.
I've been playing around with this combo of amplification for about 4 or 5 years now and just love the sound.
I was looking around for a power transformer to use in an upcoming project and stumbled across the first thing I ever “designed” basically a floating paraphrase 6SL7 driving 6BL7 with no feedback. I put it together 30 years ago or so with nothing but old parts. I opened it up today and it was not as horrifying as I figured it would be but still entertaining enough. I remember just swapping secondary leads on the on the output transformers until it sounded right with 8 Ohm speakers. Still not even sure what those transformers are or what their impedance ratio was. So…. for your viewing pleasure, here are some photos of my first hack job
I love it! Nice job👍
Wow! I'll bet that wasn't a cheap slab of metal
What's that amp weigh? About 100kg?
I did not weight it yet.
I went to California for a week visiting my family, and worked on the amp a bit. Will weight it later, when come again and finish.
You can easily identify the correct impedance ratio on those mystery transformers by applying a small ac voltage and measuring the output voltages and then use a little simple math. Here's a very easy to understand page on how to do it. Great fast reading.:I remember just swapping secondary leads on the on the output transformers until it sounded right with 8 Ohm speakers. Still not even sure what those transformers are or what their impedance ratio was.
Output Transformer Impedance
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I had a pair of this black Hammond 1555 cast aluminium boxes laying around for some time, thinking of building a small "few watter" SET amplifier.
So i started to plan the layout and drill the holes yesterday and now, finally, i can hear the sweet sweet music from this puppy!
A 6SN7 (Haltron) drives the two 6V6G (SER, Sweden) in triode mode, about 40mA current.
Voltage regulator is a Forsell variety, drops just about 40V so the B+ is 300V
The output transformers are the nice german Audioroehrentechnik 53.05U
Output power is a solid watt or two, it drives my Klipsch RF280 fairly well (97dB)
The preamp to the right is a Aikano preamplifier PCB with ECC802S.
So i started to plan the layout and drill the holes yesterday and now, finally, i can hear the sweet sweet music from this puppy!
A 6SN7 (Haltron) drives the two 6V6G (SER, Sweden) in triode mode, about 40mA current.
Voltage regulator is a Forsell variety, drops just about 40V so the B+ is 300V
The output transformers are the nice german Audioroehrentechnik 53.05U
Output power is a solid watt or two, it drives my Klipsch RF280 fairly well (97dB)
The preamp to the right is a Aikano preamplifier PCB with ECC802S.
Attachments
The MK3 prototype has been tested for a month of regular use and it is working well with no issues to note and it sounds great.
Also got a quartet of 6CA7's to try. They sound great. I think they may have slightly more gain as I initially perceived them as sounding better than the EL34's and KT77's but having retried the others, I don't think there is much in it between all three.
I'm still working on the "how to build an all metal chassis" issue. I'm torn between the simpler 3mm aluminium plate on a wooden frame like I've already build against an all metal box like a Hammond 1444 folded aluminium chassis. Landfall Systems make an extremely good looking chassis but I think shipping and taxes to the UK are likely to be painful.
Also got a quartet of 6CA7's to try. They sound great. I think they may have slightly more gain as I initially perceived them as sounding better than the EL34's and KT77's but having retried the others, I don't think there is much in it between all three.
I'm still working on the "how to build an all metal chassis" issue. I'm torn between the simpler 3mm aluminium plate on a wooden frame like I've already build against an all metal box like a Hammond 1444 folded aluminium chassis. Landfall Systems make an extremely good looking chassis but I think shipping and taxes to the UK are likely to be painful.